If the value of a is None, interpolate '', not 'None'.

2 files changed, 9 insertions, 1 deletions

diff --git a/src/engine/SCons/Util.py b/src/engine/SCons/Util.py
index 00a8330..64930b0 100644
--- a/src/engine/SCons/Util.py
+++ b/src/engine/SCons/Util.py
@@ -177,7 +177,11 @@ def scons_subst(string, locals, globals):
         if key[:1] == '{' and key[-1:] == '}':
             key = key[1:-1]
 	try:
-	    s = str(eval(key, locals, globals))
+            e = eval(key, locals, globals)
+            if e is None:
+                s = ''
+            else:
+                s = str(e)
 	except NameError:
 	    s = ''
 	return s
diff --git a/src/engine/SCons/UtilTests.py b/src/engine/SCons/UtilTests.py
index 7df0c83..f8829da 100644
--- a/src/engine/SCons/UtilTests.py
+++ b/src/engine/SCons/UtilTests.py
@@ -84,6 +84,7 @@ class UtilTestCase(unittest.TestCase):
         loc['sources'] = PathList(map(os.path.normpath, [ "./foo/blah.cpp",
                                                           "/bar/ack.cpp",
                                                           "../foo/ack.c" ]))
+        loc['xxx'] = None
 
         if os.sep == '/':
             def cvt(str):
@@ -123,6 +124,9 @@ class UtilTestCase(unittest.TestCase):
         newcom = scons_subst("test ${target.dir}", loc, {})
         assert newcom == cvt("test foo")
 
+        newcom = scons_subst("test $xxx", loc, {})
+        assert newcom == cvt("test "), newcom
+
 
 
 if __name__ == "__main__":